/*
  * Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include <unistd.h>
 #include <fcntl.h>
 #include "timer.h"

 #include "time.h"

 #include "random_seed.h"

 #include "avutil.h"

 static int read_random(uint32_t *dst, const char *file)
 {
     int fd = open(file, O_RDONLY);
     int err = -1;
 
     if (fd == -1)
         return -1;

     err = read(fd, dst, sizeof(*dst));

     close(fd);
 
     return err;
 }
 

 static uint32_t get_generic_seed(void)
 {

     clock_t last_t=0;

     int bits=0;
     uint64_t random=0;

     unsigned i;

     float s=0.000000000001;

 
     for(i=0;bits<64;i++){

         clock_t t= clock();
         if(last_t && fabs(t-last_t)>s || t==(clock_t)-1){
             if(i<10000 && s<(1<<24)){
                 s+=s;

                 i=t=0;
             }else{
                 random= 2*random + (i&1);
                 bits++;
             }
         }
         last_t= t;
     }
 #ifdef AV_READ_TIME
     random ^= AV_READ_TIME();
 #else
     random ^= clock();
 #endif
 
     random += random>>32;
 
     return random;
 }
 

 uint32_t av_get_random_seed(void)

 {
     uint32_t seed;

     if (read_random(&seed, "/dev/urandom") == sizeof(seed))
         return seed;
     if (read_random(&seed, "/dev/random")  == sizeof(seed))

         return seed;

     return get_generic_seed();

 }